Fish: wherever we go, we are told that we should eat more of it. The NHS recommends eating at least two servings of fish per week to obtain beneficial fish vitamins and omega-3 oils. Fitness blogs, cookbooks, and even movie stars all encourage people to eat more fish. But fish stocks are not a bottomless resource, and with almost a third of our fish-stocks over-exploited, we are getting close to that bottom1. Clearly, if we want to continue eating fish, something has to change.
But what can you do? Your fish purchasing choices can directly support sustainable fisheries or further encourage unsustainable fishing practices. To help make your choices, let’s learn how fish get from the sea to your local supermarket.
Humans have caught fish directly from the ocean for centuries, but as demand has increased, fishing boats have begun using unsustainable mass fishing methods. The most popular of these methods, trawling, is when large nets are dragged behind fishing vessels. When trawling, a huge amount of what is captured is bycatch, animals caught by accident when fishing for a specific species2 (Figure 1). Bycatch almost all die, mostly through suffocation in nets or on boat decks, resulting in a huge death toll of many species, including endangered species such as turtles, dolphins, and sharks2 (Figure 2). Bottom trawling, where nets are dragged along the bottom of the ocean floor, is even more destructive, since the nets stir up the seabed, killing bottom-dwelling animals and sending mud and dust particles into the water.
Figure 1: Bycatch on the deck of a ship (photo).
Figure 2: A shark caught in a trawling net (photo).
Another method of capturing wild-caught fish is long-line fishing, where lines with many baited hooks are placed in the water. The bait attracts animals indiscriminately, resulting in bycatch. Furthermore, the bait is often fish or squid, increasing the need for fishing. However, longline fishing produces 2-5 times less bycatch than trawling3. It also encourages fishermen to actively work to reduce bycatch, as each hook occupied by bycatch is one less hook available for the target fish3.
Fishing is also very hard to monitor, since fish populations are difficult to assess as they are underwater and spread out. Because of this, deciding where and how much to fish becomes a guessing game. Many times we only discover we have overfished an area until after it has occurred. Organizational bodies, such as the Marine Stewardship Council (MSC), attempt to monitor fisheries and certify sustainable ones, but this is a difficult task, and it is likely that not all MSC-certified fisheries are sustainable4. So far, the MSC has no evidence that its certification has positive environmental impacts4.
As oceans struggle to keep up with the huge demand for fish, fish farming has been quickly growing, and currently produces almost half the global fish production1,5. Fish farming uses pens or cages directly in the ocean, usually along the coast, to grow various species of fish, including salmon, cod, halibut, and Bluefin tuna (Figure 3)5. Fish farming seems to solve the problems with fishing: there is no bycatch, and it is easy to assess the size and health of farmed fish populations, preventing blind overconsumption. However, fish farming has its own problems that need to be taken into consideration.
Figure 3: A fish farm (photo).
First of all, fish farming is not as divorced from wild fishing as it seems. Many farmed fish are carnivores that are fed wild-caught fish5 (Figure 4). In fact, approximately one in six wild-caught fish is consumed by farmed fish5. Fish farming is therefore directly tied to, and dependent on, the wild fishing industry and all of its problems5.
Figure 4: Farmed fish being fed wild-caught fish (photo).
Another problem involves interbreeding between wild and farmed fish. Wild fish form subpopulations of fish optimized for specific habitats5. Farmed fish are transported across the world, and as such are not optimized for the habitat they are being farmed in5. This becomes a problem when farmed fish escape or when eggs drift out of cages and hatch. These escaped fish can breed with wild fish and produce offspring that are less optimized for their habitat, reducing the overall fitness of the subpopulation5. If this occurs for long enough, the subpopulation could become so unfit that it goes extinct.
Fish farming also affects its immediate environment. Waste from fish farms is allowed to flow freely away, contaminating local water sources5. If fish farms are placed in shallow waters, they can also kill local plants and algae.
As such, fish farming is not currently more sustainable than wild fishing, and many changes need to occur before it is. While fish farming may be effective for animals like mussels, which feed themselves and cannot escape easily, for fish, especially carnivorous fish, it still has many drawbacks.
So what should you buy?
Now that we know the different ways that fish can get to supermarkets, let’s use what we learned to purchase responsibly sourced fish! A good rule of thumb is to:
- Prioritize wild-caught fish over farmed fish
- Prioritize longline-caught fish over trawl-caught fish
- Use Figure 4 as a general guide
Figure 4: General sustainable fishing purchasing guide. Fish purchase suggestions are generalizations and may differ for individual fish species. Positives and negatives in this case simply refer to sustainability, and do not account for other positives and negatives (such as time investments or economic benefits) that influence fishing or fish farming decisions.
Information on labels, such as where the fish were caught or the MSC certification logo, can also help you decide. However, remember that buzzwords like “sustainable” can be used with little to back it up, and that the presence or absence of the MSC logo does not necessarily dictate if a fishery is sustainable or not.
Remember also that each fish species is different, and some fish are fished sustainably in one place and unsustainably in another. If you want more information about specific fish, a helpful source is the Seafood Watch App made by Monterey Bay Aquarium, which ranks both fish and sources based on their sustainability.
So next time you’re at the supermarket, looking for fish for dinner, spend a few extra seconds considering how the fish got there. Your smart sustainable choices will help ensure that those fish will still be in the ocean and in supermarkets for many years to come!
- Food and Agriculture Organization of the United Nations. (2016). The State of World Fisheries and Aquaculture.
- Davies, R. W. D., Cripps, S. J., Nickson, A., & Porter, G. (2009). Defining and estimating global marine fisheries bycatch. Marine Policy, 33(4), 661-672.
- Grekov, А. А., & Pavlenko, А. А. (2011). A comparison of longline and trawl fishing practices and suggestions for encouraging the sustainable management of fisheries in the Barents Sea. Consolidated text of all NEAFC recommendations on regulating bottom fishing.
- Ponte, S. (2012). The Marine Stewardship Council (MSC) and the making of a market for ‘sustainable fish’. Journal of Agrarian Change, 12(2‐3), 300-315.
- Goldburg, R., & Naylor, R. (2005). Future seascapes, fishing, and fish farming. Frontiers in Ecology and the Environment, 3(1), 21-28.